Comparison of Intravascular Ultrasound and X-ray Computed Tomography of the Thoracic Aorta: Correlation with Ischemic Heart Disease and Risk Factors

To compare plaque and calcification of the thoracic aorta with ischemic heart disease and risk factors, the authors used intravascular ultrasound (IVUS) and X-ray computed tomography (CT). The study included 29 patients (24 males and 5 females, mean age 61 ± 11 years): 21 with ischemic heart disease (IHD) and 8 with valvular disease or dilated cardiomyopathy. A Sonicath Ultra 6 imaging catheter (12.5 MHz, Scimed) was inserted through the femoral artery, and IVUS images were obtained around the descending aorta at the level of the pulmonary artery bifurcation. Percent plaque area (%PA) was calculated as vessel cross sectional area (CSA) surrounded by media minus lumen CSA divided by vessel CSA. The CVIS clear view system (Scimed) was used for image analysis. CT without contrast enhancement was performed from the aortic arch to the diaphragm in horizontal sections of 1 cm. The number of slices showing aortic calcification was determined as the CT calcification score. Coronary angiography (CAG) was also performed in each patient, and the authors analyzed the correlation of these imaging modalities with IHD with multiple risk factors. In the descending aorta the IVUS probe was not eccentric and gave accurate images of plaque. In the ascending aorta or aortic arch, the probe was somewhat eccentric. Plaque was observed to be diffuse without discrete lesions. The %PA was 2.5–28.6 (14.9 ± 5.5) %, and the CT score was 0–25 (8.2 ± 7.9). The %PA and CT score showed a significant correlation with each other (r = 0.57, p <0.05) and with age (r = 0.44 and 0.64, respectively, p <0.05). Neither showed a significant correlation with findings from CAG or risk factors. IVUS accurately detects the presence and extent of plaque in the thoracic aorta. The %PA shows a significant correlation with CT-detected calcification of the aorta. Neither calcification nor plaque is correlated with IHD or risk factors. IVUS-detected plaque and CT-detected calcification are strongly influenced by age.